Often, it is desirable to control the brightness of LED luminaires. Some LED luminaire drivers have been designed to provide variable power to LEDs to obtain a dimming effect. Such drivers may provide variable power in response to a user input or according to a predetermined schedule that is implemented by a controller. In known designs for driving one or more LEDs in a dimmable manner, the lamp driver receives power from a power supply (such as residential or commercial power supplied by an electric utility) to power circuit element(s) that develop a driving current.
Different methods for controlling the brightness of an LED luminaire may be employed. One such method for dimming uses the IEC (i.e., the International Electrotechnical Commission) 0-10V analog lighting control protocol (IEC standard 60929, Annex E, entitled “Control Interface for Controllable Ballasts” (© IEC:2006)). The 0-10V analog lighting control protocol specifies a direct current (DC) voltage level between about zero volts and about 10 volts as a control signal. The voltage level corresponds to an amount of dimming to be applied to the controlled LED luminaire. Furthermore, there are several variations of the IEC protocol. These variations arise with respect to how current is sourced and the voltage range utilized for the control signal.
The voltage level provided as a control signal is only capable of controlling one parameter of the controlled luminaire, namely dimming level. The implications of this characteristic on a lighting system of lower complexity, e.g. having only a handful of controlled luminaires, may seem unrestrictive. However, as lighting systems grow in complexity such systems may require a supervisory controller and multiple intermediate control modules for developing control signals. In addition to the complexity of various interconnection schemes, wiring for more sophisticated systems may require expensive and difficult to use components, such as multi-wire cables, specialized connectors, large junction boxes, and the like.
The requirement that, at some branch in the control scheme, a hardwired connection is necessary to deliver each voltage level eventually limits the practicality of the 0-10V analog lighting control protocol. Further complications arise when this limitation, namely that each voltage level used for control must be transmitted by a dedicated hardwired connection from a supervisory controller, is combined with the limitation that only dimming level may be controlled. Therefore, a need exists for a control scheme capable of communicating additional control through the existing hardware of a system utilizing the 0-10V analog lighting control protocol.
With advent of luminaires that incorporate programmable elements, there arises the capability to control luminaires in more flexible ways. One could, for example, command one or more luminaires to adjust color temperature or hue, display one or more scenes, implement scheduled lighting conditions, and the like. Such commands could be developed and transmitted using a dimmer that implements the IEC standard noted above, but this would undesirably eliminate the standard dimming capability and render the dimmer unsuitable for non-LED light sources. An alternative is to retain the conventional dimmer and dimming capability and add additional conductors and/or communication channels to provide paths for the additional commands. Such an approach undesirably adds cost and complexity to the resulting lighting system.